Clean up stale issue references in comments (gt-z5bri)

- daemon.go: Update gt-2hzl4 comment to past tense (timeout fallback is implemented)
- lifecycle.go: Remove "to be removed" promise for gt-psuw7 (code stays)
- keepalive_test.go: Remove tombstoned gt-gaxo epic reference
- doctor.go: Remove tombstoned gt-gaxo epic reference
- daemon_test.go: Remove tombstoned gt-gaxo epic reference

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/cmd/doctor.go

@@ -102,7 +102,6 @@ func runDoctor(cmd *cobra.Command, args []string) error {
 	d.Register(doctor.NewAgentBeadsCheck())
 
 	// NOTE: StaleAttachmentsCheck removed - staleness detection belongs in Deacon molecule
-	// See gt-gaxo epic for ZFC cleanup rationale
 
 	// Config architecture checks
 	d.Register(doctor.NewSettingsCheck())